Rationality: What It Is, Why It Seems Scarce, Why It Matters

by Steven Pinker

They can claim that no Scotsman puts sugar on his porridge, and when confronted with Angus, who puts sugar on his porridge, say this shows that Angus is not a true Scotsman. The no true Scotsman

These tactics shade into begging the question, a phrase that philosophers beg people not to use as a malaprop for “raising the question” but to reserve for the informal fallacy of assuming what you’re trying to prove.

One can always maintain a belief, no matter what it is, by saying that the burden of proof is on those who disagree. Bertrand Russell responded to this fallacy when he was challenged to explain why he was an atheist rather than an agnostic, since he could not prove that God does not exist. He replied, “Nobody can prove that there is not between the Earth and Mars a china teapot revolving in an elliptic orbit.”

In reality, since we start out ignorant about everything, the burden of proof is on anyone who wants to show anything.

Another diversionary tactic is called tu quoque, Latin for “you too,” also known as what-aboutery. It was a favorite of the apologists for the Soviet Union in the twentieth century,

In their article “The Nobel Disease: When Intelligence Fails to Protect against Irrationality,” Scott Lilienfeld and his colleagues list the flaky beliefs of a dozen science laureates, including eugenics, megavitamins, telepathy, homeopathy, astrology, herbalism, synchronicity, race pseudoscience, cold fusion, crank autism treatments, and denying that AIDS is caused by HIV.16

the bandwagon fallacy exploits the fact that we are social, hierarchical primates. “Most people I know think astrology is scientific, so there must be something to it.”

The history books are filled with manias, bubbles, witch hunts, and other extraordinary popular delusions and madnesses of crowds.

Another contamination of the intellectual by the social is the attempt to rebut an idea by insulting the character, motives, talents, values, or politics of the person who holds it. The fallacy is called arguing ad hominem, against the person.

Often the expression is more genteel but no less fallacious. “We don’t have to take Smith’s argument seriously; he is a straight white male and teaches at a business school.”

A related tactic is the genetic fallacy, which has nothing to do with DNA but is related to the words “genesis” and “generate.” It refers to evaluating an idea not by its truth but by its origins.

the ad hominem and genetic fallacies are genuinely fallacious: good people can hold bad beliefs and vice versa.

the increasingly popular affective fallacy, in which a statement may be rejected if it is “hurtful” or “harmful” or may cause “discomfort.”

It reflects a shift in one’s conception of the nature of beliefs: from ideas that may be true or false to expressions of a person’s moral and cultural identity.

The difference is that in the legitimate arguments, one can give reasons for why the context of a statement should affect our credence in whether it is true

With the fallacies, one is surrendering to feelings that have no bearing on the truth of the claim.

One reason logic will never rule the world is the fundamental distinction between logical propositions and empirical ones,

It’s often said that the Scientific Revolution of the seventeenth century was launched when people first appreciated that statements about the physical world are empirical and can be established only by observation, not scholastic argumentation.

A second reason Leibniz’s dream will never come true lies in the nature of formal logic: it is formal, blinkered from seeing anything but the symbols and their arrangement as they are laid out in front of the reasoner. It is blind to the content of the proposition—what those symbols mean, and the context and background knowledge that might be mixed into the deliberation.

Logic, in this sense, is not rational. In the world in which we evolved and most of the world in which we spend our days, it makes no sense to ignore everything you know.

Studies of unlettered peoples by cultural psychologists and anthropologists have shown that they are rooted in the rich texture of reality and have little patience for the make-believe worlds familiar to graduates of Western schooling.

Educated Westerners have learned how to play the game of forgetting what they know and fixating on the premises of a problem—though

There’s the slippery slope fallacy: if we legalize abortion, soon we’ll legalize infanticide; if we allow people to marry an individual who is not of the opposite sex, we will have to allow people to marry an individual who is not of the same species.

The networks are called deep learning systems because of the number of layers between the input and the output (they’re not deep in the sense of understanding anything). These networks are powering “the great AI awakening” we are living through,

Deep learning networks often outperform GOFAI (good old-fashioned artificial intelligence), which executes logic-like deductions on hand-coded propositions and rules.

unlike logical inference, the inner workings of a neural network are inscrutable. Most of the millions of hidden units don’t stand for any coherent concept that we can make sense of, and the computer scientists who train them can’t explain how they arrive at any particular answer.

The brain has around a hundred billion neurons connected by a hundred trillion synapses, and by the time we are eighteen we have been absorbing examples from our environments for more than three hundred million waking seconds. So we are prepared to do a lot of pattern-matching and associating, just like these networks.

Human rationality is a hybrid system.38 The brain contains pattern associators that soak up family resemblances and aggregate large numbers of statistical clues. But it also contains a logical symbol manipulator that can assemble concepts into propositions and draw out their implications. Call it System 2, or recursive cognition, or rule-based reasoning.

In the social sphere, our pattern-finders easily see the ways in which people differ: some individuals are richer, smarter, stronger, swifter, better-looking, and more like us than others. But when we embrace the proposition that all humans are created equal (“if X is human, then X has rights”), we can sequester these impressions from our legal and moral decision making, and treat all people equally.

An essential part of rationality is dealing with randomness in our lives and uncertainty in our knowledge.

As we shall see, mistaking a nonrandom pattern for a nonrandom process is one of the thickest chapters in the annals of human folly, and knowing the difference between them is one of the greatest gifts of rationality that education can confer.

In theory, couldn’t the demon imagined by Pierre-Simon Laplace in 1814, who knew the position and momentum of every particle in the universe, plug them into equations for the laws of physics and predict the future perfectly?

the butterfly effect, named after the possibility that the flapping of a butterfly’s wings in Brazil could trigger a tornado in Texas.

where minuscule differences in initial conditions, too small for any instrument to measure, can feed on themselves and blow up into gargantuan effects.

There is the classical definition of probability, which goes back to the origins of probability theory as a way of understanding games of chance. You lay out the possible outcomes of a process that have an equal chance of occurring, add up the ones that count as examples of the event, and divide by the number of possibilities.

subjectivist interpretation. Before you fling the die, based on everything you know, how would you quantify, on a scale from 0 to 1, your belief that it will land even? This credence estimate is sometimes called the Bayesian interpretation of probability

Then there is the evidential interpretation: the degree to which you believe the information presented warrants the conclusion.

Finally there is the frequentist interpretation: if you did toss the die many times, say, a thousand, and counted the outcomes, you’d find that the result was even in around five hundred of the tosses, or half of them.

reframing a probability from credence in a single event to frequency in a set of events can recalibrate people’s intuitions.

Despite the difference in interpretations, probability is intimately tied to events as a proportion of opportunities,

To estimate risk, we should tally the number of instances of an event and mentally divide it by the number of occasions on which it could have taken place. Yet one of the signature findings in the science of human judgment is that this is not how human probability estimation generally works.

The heuristic exploits a feature of human memory, namely that recall is affected by frequency: the more often we encounter something, the stronger the trace it leaves in our brains.

With the rise of liberal democracies in the nineteenth century, data came to be considered a public good.12 Even today, when data on just about everything is a few clicks away, not many people avail themselves of it.

Outside our immediate experience, we learn about the world through the media. Media coverage thus drives people’s sense of frequency and risk: they think they are likelier to be killed by a tornado than by asthma, despite asthma being eighty times deadlier, presumably because tornadoes are more photogenic.13 For similar reasons the kinds of people who can’t stay out of the news tend to be overrepresented in our mental censuses. What percentage of teenage girls give birth each year, worldwide? People guess 20 percent, around ten times too many.

Other than disease, the most lethal risk to life and limb is accidents, which kill about five million people a year (out of 56 million deaths in all), about a quarter of them in traffic accidents.16 But except when they take the life of a photogenic celebrity, car crashes seldom make the news, and people are insouciant about the carnage. Plane crashes, in contrast, get lavish coverage, but they kill only about 250 people a year worldwide, making planes about a thousand times safer per passenger mile than cars.

Several eminent climate scientists, having crunched the numbers, warn that “there is no credible path to climate stabilization that does not include a substantial role for nuclear power.”21 Nuclear power is the safest form of energy humanity has ever used. Mining accidents, hydroelectric dam failures, natural gas explosions, and oil train crashes all kill people, sometimes in large numbers, and smoke from burning coal kills them in enormous numbers, more than half a million per year.

In large part the opposition is driven by memories of three accidents: Three Mile Island in 1979, which killed no one; Fukushima in 2011, which killed one worker years later (the other deaths were caused by the tsunami and from a panicked evacuation); and the Soviet-bungled Chernobyl in 1986, which killed 31 in the accident and perhaps several thousand from cancer, around the same number killed by coal emissions every day.

in most bad years, the United States suffers a few dozen terrorist deaths, a rounding error in the tally of homicides and accidents. (The annual toll is lower, for example, than the number of people killed by lightning, bee stings, or drowning in bathtubs.)

These upheavals were driven by the impression that African Americans are at serious risk of being killed by the police. Yet as with terrorism and school shootings, the numbers are surprising. A total of 65 unarmed Americans of all races are killed by the police in an average year, of which 23 are African American, which is around three tenths of one percent of the 7,500 African American homicide victims.

Homicide is not like other lethal hazards. A hurricane or shark doesn’t care how we will respond to the harm they have in store for us, but a human killer might.